1. Technical Field
The present invention relates to methods and apparatus for protecting glass windows and doors from damage due to storms, vandals, and burglars.
2. Discussion of the Prior Art
In geographic areas that are subject to storms of hurricane force it is common to protect glass windows and doors with storm shutters capable of being positioned in front of the outside surface of the glass. Typically, such shutters are made of opaque metal, wood or plastic and configured to be pivoted, slid or rolled into and out of position so that people inside the structure can see out through the glass when there is no storm danger. The need to move these types of shutters into protective position is undesirable. Specifically, if a sudden storm arises, particularly when all occupants are temporarily out of the structure, the windows or doors may be left unprotected. In addition, although some prior art storm shutters are capable of protecting against vandals and burglars, this function is only served when the shutters are moved into position over the glass door or window. Clearly, one could keep the shutters deployed over the door or window at all times and thereby attain permanent protection against storms, vandals, burglars, etc.; however, this would permanently block transmission of light into the structure, thereby nullifying the very purpose of having glass doors and windows.
In U.S. Pat. No. 4,685,261 (Seaquist) there is disclosed a storm shutter comprising a pair of shatter-resistant, translucent panels mounted securely in an aluminum frame that is slidably engaged in brackets secured to the outside of the structure above and below the protected window. The frame is primarily intended to be removed from the brackets when a storm danger has passed, but the patent suggests that the frame may be permanently secured to the brackets. If the frame is permanently secured, the distortion of light provided by the translucent panels is highly undesirable. Moreover, since the translucent panels are fixedly positioned in the frame, an occupant of the structure achieves no ventilation by opening the protected glass window. On the other hand, if the frame is removable from the brackets, it may not happen to be in place to protect the window when sudden storms arise. Further, if not permanently secured to the brackets, the shutter is no deterrent to vandals and burglars. Finally, and of crucial importance, the polycarbonate translucent panels are firmly engaged in an aluminum frame without any allowance for expansion of the panels relative to the frame. Since the coefficient of thermal expansion of polycarbonate is approximately three times that of aluminum, variations in sheet size in response to temperature changes can tear or buckle the aluminum frame.
A protective enclosure for windows disclosed in U.S. Pat. No. 4,175,357 (Goldhaber) includes a shatter-resistant, transparent plastic sheet tightly secured in a metal frame. The frame is mounted for pivotal motion in front of a conventional window and can be supported in an open pivot position to permit outside air to pass through the protected window when the latter is open. A latch, accessible only from inside the protected space, must be actuated before the frame can be pivoted outwardly. Accordingly, this unit satisfactorily protects against burglars and vandals while transmitting light without distortion. However, although the unit can be pivoted to an open position, the resulting opening is not directly aligned with openings in the protected window, thereby limiting the effectiveness of the opening for purposes of ventilation. Of greater importance, however, is the fact that the unit does not provide for the different coefficients of thermal expansion of the plastic sheet and its surrounding frame. Accordingly, the frame is subject to damage from different rates of expansion at extreme ambient temperatures.
Another transparent protective unit is disclosed in U.S. Pat. No. 4,562,666 (Young III). In this unit an unframed sheet of substantially unbreakable transparent polycarbonate is secured to the frame of a conventional window inside the building. Since the sheet itself has no frame, there is no danger of damage resulting from extreme temperature variations. It should be noted, however, that since the unframed transparent sheet is located inside the building, it is subjected to very small variations in temperature in any event. Of course, by being so located, the unit does not protect the conventional window against breakage but instead merely serves to prevent burglars from entering the building through the broken window. If the cause of window breakage happens to be a storm, the mounting arrangement for the polycarbonate sheet is such that it will not prevent wind and rain from entering via the broken window and gaps located between the window frame and the protective unit.
What is clearly lacking in the prior art, therefore, is a transparent storm shutter capable of protecting a glass window or door without being subject to damage caused by different rates of thermal expansion for its component parts, namely the transparent panel and its surrounding frame. Further, the prior art lacks a storm shutter having these features plus the capability of being selectively opened to permit air to flow directly through the protected window when the latter is open.